Jet fuel and motor fuel production by hydrofining and two stage hydrocracking

ABSTRACT

HIGH QUALITY JET AND MOTOR FUELS ARE PREPARED BY HYDROTREATING A HYDROCARBON OIL CHARGE STOCK, PASSING THE EFFLUENT FROM THE HYDROTREATING ZONE INTO CONTACT WITH A HYDROCRACKING CATALYST COMPRISING A GROUP VIII METAL SUPPORTED ON A MODIFIED ZEOLITE AND AT LEAST ONE AMORPHOUS INORGANIC OXIDE, RECOVERING A MOTOR AND A JET FUEL FRACTION AND CONTACTING THAT PORTION OF THE PRODUCT BOILING ABOVE THE JET FUEL RANGE WITH A NICKEL HYDROCRACKING CATALYST.

United States Patent U.S. Cl. 208-89 7 Claims ABSTRACT OF THE DISCLOSUREHigh quality jet and motor fuels are prepared by hydrotreating ahydrocarbon oil charge stock, passing the efiluent from thehydrotreating zone into contact with a hydrocracking catalyst comprisinga Group VIII metal supported on a modified zeolite and at least oneamorphous inorganic oxide, recovering a motor and a jet fuel fractionand contacting that portion of the product boiling above the jet fuelrange with a nickel hydrocracking catalyst.

This application is a continuation of Ser. No. 739,140 filed June 24,1968, now abandoned.

This invention is concerned with the conversion of hydrocarbon oils.More particularly, it is concerned with the hydrocracking of heavyhydrocarbon oils into lighter products. In a more specific aspect, it isconcerned with the production of high octane motor fuel and high qualityjet fuel simultaneously from higher boiling hydrocarbon oils.

The hydrocracking of petroleum oils has been known for many years andwas practiced, although not too successfully in Europe several decadesago. However with the development of new catalysts and new operatingtech niques, it has been improved to the stage where it has attainedcommercial significance and is now being used in many refineries. In theearly days of its commercial use, hydrocracking was designed exclusivelyfor the production of motor fuel or gasoline. Currently with theincreased demand for jet fuel, which can no longer be met by the supplyof straight run kerosene, attempts have been made to adapt hydrocrackingof heavy oils to the production of jet fuel as well as the production ofmotor fuel. Unfortunately, the sophisticated present day jet enginerequires specific characteristics in a jet fuel just as the sparkignition engine requires specific characteristics in a motor fuel.

The characteristics of high quality jet fuel are entirely different fromthose of high octane motor fuel, the prime dilference being thataromatics are a desirable component of motor fuel because of their highoctane rating whereas such materials are extremely undesirable in a jetfuel as they contribute to a low luminometer number indicating that thejet fuel will burn with a radiant flame. It is therefore hardly possibleto subject a heavy oil such as a gas oil to hydrocracking and to recoverfrom the product a low aromatic jet fuel having a high luminometernumber and also to recover from the same product a highly aromatic motorfuel having a high octane number. If a hydrocracking unit is designedand operated to produce high octane gasoline then the jet fuel fractionof the product is of inferior quality and similarly if the hydrocrackingunit is designed and operated to produce high luminometer number jetfuel then the gasoline fraction is not of high quality.

Several attempts have been made recently to produce jet fuels and motorfuels simultaneously in a two-stage 3,761,395 Patented Sept. 25, 1973type of hydrocracking process but on the whole they have beenunsatisfactory in that an undesirably large volume of fixed gases hasbeen produced in the first stage, and the feed stock sent to the secondstage has been of poor quality for second stage conversion.

It is therefore an object of the present invention to provide a novelhydrocracking process. Another object is to provide a process for thesimultaneous production of motor fuel and jet fuel in a hydrocrackingunit. Still another object of the invention is to provide a noveltwostage hydrocracking process in which different catalysts are used ineach stage. Another object of the invention is to provide a two-stagehydrocracking process in which relatively small amounts of fixed gasesare produced in the first stage and a suitable charge stock is sent tothe second stage. These and other objects will be obvious to thoseskilled in the art from the following disclosure.

In accordance with the above objects, our invention provides a processfor the simultaneous production of a high quality jet fuel and highoctane motor fuel which comprises passing a hydrocarbon oil into contactwith a. hydrotreating catalyst under hydrotreating conditions, passingthe entire efiluent from the hydrotreating zone into contact in a firststage with a hydrocracking catalyst comprising a Group VIII metal on asupport comprising a modified zeolite and at least one amorphousinorganic oxide under hydrocracking conditions, separating a motor fueland a jet fuel from the first stage efiluent, passing that portion ofthe effluent boiling above the jet fuel range into contact in a secondstage with a hydrocracking catalyst comprising nickel on a crackingsupport under hydrocracking conditions and recovering a motor fuelfraction from the second stage efiluent.

The charge stocks suitable for processing include heavy petroleumhydrocarbon oils such as straight run gas oil, fluid catalyticallycracked cycle gas oil, atmospheric residuum, shale oil, tar sand oil,delayed coker gas oil, crude oil, mixtures thereof and the like.

The hydrogen used in the process of our invention need not necessarilybe pure. The hydrogen content of the hydrogenating gas should be atleast about 60% and is preferably at least about by volume. Particularlysuitable sources of hydrogen are catalytic reformer byproduct hydrogenand hydrogen produced by the partial combustion of a carbonaceousmaterial followed by shift conversion and CO removal. Hydrogen rates areexpressed in terms of standard cubic feet per barrel of charge to thereactor, viz. s.c.f.b.

The catalyst used in the hydrotreating reactor should have goodhydrotreating activity but little, if any, cracking activity. Suitablecatalysts comprise a hydrogenating component as for example the oxide orsulfide of cobalt, nickel, iron, molybdenum, tungsten, chromium,vanadium and mixtures thereof on a support such as silica, alumina,zirconia, magnesia and mixtures thereof used as such or in conjunctionwith zeolites not necessarily of reduced alkali metal content. Preferredcatalysts comprise nickel tungsten on boria promoted alumina and nickelmolybdenum on activated alumina. The hydrogenating component should bepresent in an amount between about 5% and 40% by weight based on thecatalyst composite. Catalysts containing about 6% nickel and 20%tungsten or 5% nickel oxide and 15% molybdenum oxide have been foundsatisfactory. When the charge is a heavy hydrocarbon oil containing forexample at least 1% Conradson carbon residue then advantageously thecatalyst support will contain at least 2% silica and will have a minimumsurface area of 250 square meters per gram and a minimum pore volume of0.6 cc. per gram.

The charge together with hydrogen is introduced into the hydrotreatingzone which is maintained at a temperature between about 550 and 900 F.and a pressure between 200 and 10,000 p.s.i.g. The hydrocarbon charge isintroduced at a liquid hourly space velocity between 0.2 and volumes ofoil per volume of catalyst per hour and the hydrogen is introduced at arate of between 1000 and 50,000 s.c.f.b. Preferred conditions include atemperature of 650800 F., a pressure of 5002000 p.s.i.g., a spacevelocity of 0.5-2.0 v./v./hr. and a hydrogen rate of 300010,000 s.c.f.b.The entire efiluent from the hydrotreating zone is passed to the firststage of the hydrocracking zone although in some instances it may beadvantageous to cool the effluent to a suitable hydrocrackingtemperature.

The first stage hydrocracking zone is maintained at a temperature of550900 F., preferably 650800 F. and the catalyst bed is of a sizesufficient to provide a space velocity of between 0.2 and 10 v./v./hr.,preferably 0.52- 2 v./v./ hr. The pressure within the first stagehydrocracking zone is substantially the same as the pressure in thehydrotreating zone, sufficient pressure drop being taken to maintain theflow of reactants through the system.

The catalyst used in the first stage hydrocracking zone contains twocomponents, a hydrogenating component supported on a cracking component.Suitable hydrogenating components comprise metals and compounds ofmetals of Group VIII, e.g. the noble metals particularly platinum andpalladium, and the iron group metals, particularly cobalt and nickel.Advantageously the catalyst may also contain a Group VI metal, e.g.molybdenum or tungsten used in conjunction with the iron group metal.The hydrogenating component may be used either in the metallic form orin the form of a compound, e.g. the oxide, sulfide or telluride.

The cracking component of the catalyst comprises a modified crystallinezeolite and at least one amorphous inorganic oxide, the modified zeolitebeing present in an amount between about and 60% by weight. Suitableamorphous inorganic oxides are those displaying cracking activity suchas silica, alumina, magnesia, zirconia and beryllia which if necessaryhas been treated with an acidic agent such as hydrofluoric acid toimpart cracking activity thereto. A preferred mixture of amorphousinorganic oxides comprises silica-alumina in a proportion ranging from6090% silica and 1040% alumina.

The modified zeolite portion of the cracking component has uniform poreopenings of from 6-15 angstrom units, has a silica-alumina ratio of atleast 2.5, e.g. 3-10, and has a reduced alkali metal content. Themodified zeolite is prepared by subjecting synthetic zeolite Y to ionexchange by contacting the zeolite several times with fresh solutions ofan ammonium compound at temperatures ranging between about 100 and 250F. until it appears that the ion exchange is substantially complete. Theion exchanged zeolite is then washed to remove solubilized alkali metaland dried at a temperature sufficiently high to drive off ammonia. Thistreatment converts the zeolite Y to the hydrogen form and reduces thealkali metal content to about 2-4 weight percent. The ion exchangedzeolite is then calcined at a temperature of about 1000 F. for severalhours. After cooling, the ion-exchanged, calcined zeolite is subjectedto additional ion exchange by contact several times with fresh solutionsof an ammonium compound and again washed and dried. This treatmentresults in a further reduction in the alkali metal content of thezeolite to less than 1% usually to about 0.5% or less. It would appearthat after the first calcination, it is possible to engage in furtherion exchange with the removal of additional alkali-metal ions notremovable in the initial ion exchange. Calcination at e.g. 1000-1500 F.may take place here or may be postponed until after the incorporation ofthe inorganic oxide and impregnation with the hydrogenating component atwhich time the composite should be calcined. Whether the calcination ispostponed or repeated, the final calcination temperature should notexceed 1200 F.

Hydrocracking catalysts containing a hydrogenating component supportedon a cracking component composed of at least one amorphous inorganicoxide and the twice ion exchanged, twice calcined zeolite have superiorhydrocracking activity and additionally are more resistant todeactivation when brought into contact with nitrogen compounds andpolycyclic aromatics. They also show good stability to steam. Thehydrocracking catalyst should also be substantially free from rare earthmetals and should have a rare earth metal content below 0.5 weightpercent, preferably below 0.2 weight percent. It has been found thatalthough rare earth metals are reputed to enhance the activity andstability characteristics of cracking catalysts, their presence in ahydrocracking catalyst has been found to be undesirable.

When the hydrogenating component of the hydrocracking catalyst is anoble metal it should be present in an amount between about 0.2 and 5.0%by weight based on the total catalyst composite. Preferably the noblemetal is present in an amount between 0.5 and 2%. When the hydrogenatingcomponent comprises a Group VIII metal it should be present in an amountbetween about 1 and 40% by weight based on the total catalyst composite.If the iron group metal is the sole hydrogenating component, it may bepresent in an amount between about 5 and 10%. When a Group VI metal isused in conjunction with a Group VIII metal, the Group VI metal may bepresent in an amount preferably between about 5 and 30%. Particularlysuitable catalysts are those containing between 0.5 and 1.0 weightpercent noble metal and those containing between 5 and 10% iron groupmetal and between 15 and 30% Group VI metal. Specific examples ofsuitable catalysts are those containing 0.6-0.75 weight percentpalladium or containing about 6% nickel and 20% tungsten on a supportmade up of about 25% modified zeolite Y, 55% silica and 20% alumina. Thehydrogenating component may be deposited on the cracking component byimpregnating the latter with a solution of a compound of thehydrogenating component, drying and forming e.g. into pellets orextrudates. Such techniques are well known in the art and require nodescription here.

The effluent from the first stage hydrocracking zone is passed to a highpressure separation zone from which a gas rich in hydrogen is removedand recycled to the hydrotreating zone. Advantageously, a hydrogen bleedstream is taken from the recycle stream to prevent the build-up ofgaseous hydrocarbons therein. Desirably, the recycle stream is alsosubjected to a purification treatment for the removal of H 8 and NH Amake-up stream of hydrogen is introduced into the recycle stream toreplenish that portion drawn off and the hydrogen consumed in thehydrotreating zone and the first stage hydrocracking zone.

The remainder of the efiluent removed from the high pressure separatoris fractionated to separate therefrom a gasoline fraction and a jet fuelfraction. That portion of the efliuent boiling above the jet fuel rangeis introduced into the second stage hydrocracking zone with additionalhydrogen.

In the second stage hydrocracking zone the pressure is malntamed betweenabout 200 and 10,000 p.s.i.g., preferably between 500 and 2000 p.s.i.g.The temperature range 1n the second stage hydrocracking zone is SOD-900F., preferably 550800 F., hydrogen is introduced at a rate of between1000 and 50,000 s.c.f.b., a preferred rate being between 3000 and 10,000s.c.f.b. and the space velocity ls/getween 0.2 and 10 v./v./hr.,preferably 0.5-2.0 v./ v. r.

The catalyst in the second stage hydrocracking zone also contains ahydrogenating component supported on a cracking component. Thehydrogenating component is nickel, preferably in oxide form, in anamount between 4 and 20% by weight of the catalyst composite andpreferably between 5 and 10%. Advantageously the feed both hydrocarbonand hydrogen should be substantially sulfur free to avoid conversion ofthe hydrogenation component to the sulfide as the gasoline productobtained when the catalyst is in the sulfide form is somewhat inferiorto the gasoline obtained when the hydrogenating component is in theoxide form.

The cracking component may be a low alkali metal crystalline zeolite, amixture of amorphous inorganic oxides or a combination thereof.Advantageously the support may be of the same composition as the supportused in the catalyst of the first stage hydrocracking zone.

The effluent from the second stage hydrocracking zone is then separatedinto a normally liquid hydrocarbon portion and a hydrogen-rich streamwhich latter may berecycled to the second stage hydrocracking zone ormay be introduced into a common recycle stream which supplies hydrogento both the hydrotreating zone and the second stage hydrocracking zone.In the case of a common recycle stream, care should be taken to ensurethat the hydrogen fed to the second stage hydrocracking zone isessentially sulfur free, i.e. containing less than 100 p.p.m. sulfur.The normally liquid hydrocarbon portion of the effluent is separatedinto a gasoline fraction which is withdrawn as product and that portionof the efiluent boiling above the gasoline fraction including the jetfuel and heavier hydrocarbons is recycled to the second stagehydrocracking zone.

The following examples are given for illustrative purposes only and arenot to be construed as limiting the invention in any manner.

EXAMPLE I This example shows a typical conventional process for theproduction of gasoline.

The hydrotreating zone catalyst is composed of 3% nickel oxide andmolybdena on alumina. Both the first and second stage hydrocrackingcatalysts contain 0.7% palladium on a decationized zeolite Y containing2.5% Na O. The entire effluent of the hydrotreating zone is sentdirectly to the first stage hydrocracking zone.

Reaction conditions and other data are as follows:

Hydrotreating Reaction conditions: zone Temperature, F. 690 Pressure,p.s.i.g 1500 LHSV, v./v./hr. 1.0 Hydrogen rate, s.c.f.b. 6000Hydrocracking zone 1 2 Temperature, F 695 590 Pressure, p.s.i.g. 1, 5001, 500 LHSV, v./v.lhr 0. 9 1. 5 Hydrogen rate, s.c.f.b-......- 6, 000 6,000 Yields:

C1-C3, weight percent. 4. 2 i-C4, volume percent..- 7. 6 15. 0 n-C4,volume percent... 4. 7 6.0 I'Cfi, volume percent..-.- 11. 2 14.3 HCfi,volume percent 1. 5 1. 6 06-215 F., volume percent.-. 14. 5 23.4 215-400F. volume percent. 33.1 59.5 400 F. to stage 2. 46. 6

96. 9 93. 3 87. 5 75. 3 Hydrocarbon analysis, volume percent:

Paraffius 32. 9 36. 7 Cycloparatfins.. 45. 6 58. 6 21.4 4. 8

Aromatics 6 EXAMPLE n This example shows the superiority of ourprocessing scheme over that of Example I for the production of gasoline.The charge, hydrotreating catalyst and reaction conditions here are thesame as those for Example I but the first stage hydrocracking catalystcontains 6% nickel and 19% tungsten on a support composed of 26%alumina, 52% silica and 22% modified zeolite prepared by subjecting asynthetic zeolite Y to ion exchange with ammonium chloride, washing,drying and calcining at 1000 F., subjecting the treated zeolite to asecond ion-exchange with ammonium chloride, washing, drying andcalcining at 1000 F. to yield a modified zeolite containing 0.16% Na O,incorporating the silica-alumina into the modified zeolite, impregnatingthe support with a solution of nickel nitrate and after drying with asolution of ammonium metatungstate, drying, calcining at 1000 F. andthen sulfiding. The second stage hydrocracking catalyst contains 6%nickel oxide on a support composed of 73% silica and 27% alumina.

Hydrocraeking zone 1 Temperature, F 695 650 Pressure, p.s.i.g 1, 550 1,500 LHSV, v./v./hr 0. e 1. 5 Hydrogen rate, s.o.f.b.....- 6, 000 6, 000Yields:

C1-C3, weight percent 0.8 i-C4, volume percent.. 5. 7 16. 0 n-C4, volumepercent- 4. 2 8. 0 i-O volume percent...- 8.4 15.0 n-O5, volume percent2. 5 1. 1 (ls-215 F., volume percent.--. 19.9 19.2 215400" F., volumepercent- 28.8 57.9 400 F. to stage 2... 51.3

95.8 95.6 88.1 81.6 Hydrocarbon analysis, volume percent:

Paralfins 28. 4 39. 1 Oycloparatfinsnn 56. 7 45. 8 Aromatics 15. 0 15. 2

EXAMPLE III When the process of Example 11 is operated to produce jetfuel and gasoline, the operating data and yield figures appear in thetable below.

Hydrocracking zone 1 2 Temperature, F 645 Pressure, p.s.i.g. 1, 500LHSV, v./v./hr.. 1. 5 Hydrogen rate, s.e.i.b- 6, 000 6, 000 Yields:

C1-C weight percent 0.7 i-C4, volume percent 2. 2 14. 8 Il-C4, volumepercent- 1. 3 7. 3 i-O volume percent. 2. 6 14. 3 n-C volume percent1.0 1. 0 115-235 F., volume percen 10. 4 1 20. 1 235-295 F., volumepercent 8. 2 2 58. 7 295525 F., volume percent- 42. 1 525 F. to stage 249. 5 Motor fuel; Research Octane No. (+3 cc. TEL):

35. 2 37. 8 58. 8 46. 1 Aromatics 6. 0 16. 1 Jet fuel:

Smoke point, mm 23 Freezing point, F 59 Aromatics, volume percent 11ASTM distillation, F:

IB P-lOV 333-361 20-50%- 37 6-425 70-90%. 452-488 1 115-215 F. B 215-400F.

In Examples II and III, the total amount of sulfur introduced into stage2 from both hydrocarbon and hydrogen sources is less than p.p.m. basedby weight on the hydrocarbon charge.

Various modifications and variations of the invention as hereinbeforeset forth may be made without departing from the spirit and scopethereof, and therefore, only such limitations should be imposed as areindicated in the appended claims.

We claim:

1. A process for the simultaneous production of a high quality jet fueland high octane motor fuel which comprises contacting a petroleumhydrocarbon oil in a hydrofining zone with hydrogen and with ahydrofining catalyst under hydrofining conditions to convert sulfur andnitrogen impurities in said oil into hydrogen sulfide and ammonium gas,passing the entire effluent from said hydrofining zone into a firsthydrocracking stage and contacting said efiluent therein with hydrogen,and with a hydrocracking catalyst comprising an iron group metal sulfideand a Group VI metal sulfide on a support comprising a hydrogen zeolitehaving an alkali metal content of less than 0.5 wt./percent, a rareearth metal content not exceeding 0.2 wt./percent, a silica-aluminaratio of at least 2.5 and uniform pore openings of 6-15 A. prepared froman alkali metal zeolite by an alternating sequence of at least two ionexchanges with a solution of an ammonium compound and two calcinations,said support also including at least one amorphous inorganic oxideselected from the group consisting of silica, alumina, magnesia,zirconia, beryllia and mixtures thereof, separating a motor fuel and ajet fuel from the first hydrocracking stage efiluent as products of theprocess, passing that portion of said eflluent boiling above the jetfuel range into a second hydrocracking stage and contacting therein saidefiluent boiling above the jet fuel range with hydrogen and with ahydrocracking catalyst comprising a hydrogenating component consistingessentially of nickel or nickel oxide on a cracking support underhydrocracking conditions and recovering from the second hydrocrackingstage eflluent a motor fuel as product of the process.

2. The process of claim 1 in which said nickel of the secondhydrocracking stage catalyst is supported on a base comprising silicaand alumina.

3. The process of claim 1 in which the nickel of said secondhydrocracking stage catalyst is supported on a base comprising ahydrogen zeolite having an alkali metal content of less than 1%, asilica-alumina ratio of at least 2.5 and uniform pore openings of 6-15A.

4. The process of claim 1 in which the effiuent passed to the secondstage hydrocracking zone contains not more than 100 p.p.m. sulfur basedon the weight of the hydrocarbon charge.

5. The process of claim 1 in which the first stage hydrocrackingcatalyst support contains between 15 and zeolite having an alkali metalcontent of less than 0.5%, a silica-alumina ratio of at least 2.5 anduniform pore openings of 6-15A.

6. The process of claim 1 in which the hydrogenating component of thefirst stage hydrocracking catalyst comprises nickel sulfide and tungstensulfide.

7. The process of claim 1 in which the initial charge stock contains atleast 1% Conradson carbon residue and the hydrofining catalyst supportcontains at least 2% silica and has a surface area of at least 250 sq.meters per gram and a pore volume of at least 0.6 cc. per gram.

References Cited UNITED STATES PATENTS 3,669,903 6/1972 Bourguet et a1208-111 3,468,788 9/1969 Wilkinson 20889 3,132,087 5/1964 Kelley et al.208-59 3,256,178 6/1966 Hass et al. 208-89 3,354,077 11/1967 Hansford20811l 3,304,254 2/1967 Eastwood et a1 208l1l DELBERT E. GANTZ, PrimaryExaminer G. J. CRASANAKIS, Assistant Examiner

